The invention relates to a roller bearing, particularly a needle bearing, for arranging on a pivot pin of a variable guide vane of a turbomachine. Furthermore, the invention relates to a variable guide vane, a housing of a turbomachine, as well as a turbomachine.
Variable guide vanes in a turbomachine, for example in a turbine of an aircraft engine, enable one to modify the intake capability of this turbomachine. In this way, the turbomachine can be better adjusted for various operating points, whereby the efficiency increases and the fuel consumption is decreased for example.
A problem for example in airplane turbines is the mounting of the variable guide vanes, whose leak-tightness must be assured for approximately 25,000 flight cycles. It is known from DE 1931044 A for example to rotatably mount pivot pins of adjustable guide vanes by a combination of a roller bearing and a slide or ball bearing on the housing of a turbomachine.
Due to the high temperatures and temperature gradients during operation of the associated turbomachine, such slide bearings tend to “seize” after only relatively few cycles, while the roller bearings often distort and thereby damage or even destroy themselves. This can only be compensated for with a comparatively large bearing play, which, however, results in high leakage rates and correspondingly low efficiencies.
The object of the present invention is to provide a bearing for variable guide vanes of turbomachines, which ensures a precise guiding of an associated shaft even at large temperature fluctuations. Additional objects of the invention consist of providing a guide vane with such a bearing, a housing of a turbomachine with correspondingly mounted guide vanes as well as a turbomachine with such mounted guide vanes.
A bearing according to the invention, which ensures precise guiding of the associated shaft even at large temperature fluctuations, is according to a first aspect of the invention constructed as a roller bearing, particularly a needle bearing, and includes at least one radially elastic needle that has two opposing end regions, and at least one roller region arranged between the end regions and constructed in a cross-sectionally thickened manner. The end regions thereby roll off to associated raceways of a bearing housing of the roller bearing, while the roller region is arranged in the region of an associated groove of the bearing housing. A radially elastic bearing is hereby created, which by an elastic deformation of the needle can compensate for large temperature differences and tolerances between the bearing housing, which can also be described as a bearing bushing, and an associated shaft, particularly a pivot pin of a guide vane. By the precise guiding of an associated shaft, other elements, such as shaft seals for example are also protected and their leak-tightness is maintained. The elasticity and radial deformability of the needle is achieved on the one hand by the needle resting on or contacting the bearing housing, or on the other running along a groove of the bearing housing so that the roller region of the needle can move into or out of this groove under the elastic deformation of the needle. By the elastic yielding capability of the needle, an at least extensive play-free mounting of an associated guide vane is ensured in all operating points and also during transient transitions of an associated turbomachine, in which particularly large temperature variances occur. In addition, there is only a very slight bearing wear without “seizing” by the mainly occurring roll movements of the needle. The roller bearing according to the invention therefore allows a substantially more leak-tight and more durable mounting of guide vanes than previous bearings or bearing combinations.
In an advantageous embodiment of the invention, the groove is constructed in such a manner that at least one roller region does not contact the bearing housing given a needle under no load. In other words, it is provided that between a wall of the groove and the roller region of the needle, a predetermined clearance exists in the event of a needle that is not under any force or not deformed. It is hereby ensured that the needle deforms inwardly into the groove only in the event of being subjected to tension or force as the case may be or temperature, until the roller region lies against the wall of the groove. By the clearance between the wall of the groove and the roller region given a no-load needle, the maximum permissible deformation of the needle can be adjusted in a particularly simple manner.
Additional advantages emerge when at least one roller region is constructed in the middle of the needle. A particularly symmetrical force distribution across the needle is hereby achieved in the event of a radial bending of the needle, whereby the durability of the roller bearing is further increased.
In an additional advantageous embodiment of the invention, an axial length of the roller region is between 5% and 50% of the total length of the needle. In other words, the roller region has an axial elongation that corresponds to 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50% of the axial total elongation of the needle. The contact surface, located between the end regions, of the needle can hereby be optimally adapted to the respective conditions and requirements. Alternatively or additionally, it is provided according to the invention that an average cross-sectional thickness of the roller region is between 105% and 180% of the average cross-sectional thickness of the needle. In other words, it is provided that the cross-section of the roller region is on average 105%, 106%, 107%, 108%, 109%, 110%, 111%, 112%, 113%, 114%, 115%, 116%, 117%, 118%, 119% 120%, 121%, 122%, 123%, 124%, 125%, 126%, 127%, 128%, 129%, 130%, 131%, 132%, 133%, 134%, 135%, 136%, 137%, 138%, 139%, 140%, 141%, 142%, 143%, 144%, 145%, 146%, 147%, 148%, 149%, 150%, 151%, 152%, 153%, 154%, 155%, 156%, 157%, 158%, 159%, 160%, 161%, 162%, 163%, 164%, 165%, 166%, 167%, 168%, 169%, 170%, 171%, 172%, 173%, 174%, 175%, 176%, 177%, 178%, 179% or 180% of the average cross-sectional thickness of the needle. The average cross-sectional thickness of the needle thereby refers to the average cross-sectional thickness of those regions of the needle that are not part of the roller region. One can hereby adjust the bending behavior on the one hand and on the other the maximum permissible bending of the needle.
Additional advantages emerge by the roller region being constructed at least essentially in a cylindrical or spherical manner. This allows for a simple adaptation of the roller surface of the needle to the geometric design of the groove of the bearing housing.
In another embodiment of the invention, it may thereby be provided that the needle has at least two roller regions that are spaced apart from one another. The needle hereby has between its ends two or more contact surfaces, wherein a particularly precise adjustability of the bending behavior of the needle is made possible. The at least two roller regions can thereby basically have the same cross-sectional thicknesses or variable cross-sectional thickness and/or the same or different cross-sectional geometries.
In another advantageous embodiment of the invention, the needle is guided into a cage of the bearing housing, the cage limiting a relative mobility of the needle in relation to the bearing housing. In this way, the needle is guided precisely into the bearing housing and secured against falling out.
Additional advantages emerge when the bearing housing is assigned an insulation element for heat insulation purposes. The service life of the roller bearing can hereby also be advantageously increased, particularly when used in turbomachines with high temperature loads and large temperature fluctuations. For example, the insulation element can partially or entirely surround the bearing housing.
A particularly reliable mounting is achieved in another embodiment of the invention when the bearing housing includes a needle collar with multiple needles arranged in a ring-shaped manner.
A second aspect of the invention relates to a guide vane of a turbomachine, with a pivot pin on which at least one roller bearing is arranged. In doing so, it is provided according to the invention that the thereby utilized roller bearing is constructed according to the first aspect of the invention. The features resulting from this and their advantages are disclosed in the descriptions of the first aspect of the invention, wherein advantageous embodiments of the first aspect of the invention are to be considered as advantageous embodiments of the second aspect of the invention.
A third aspect of the invention relates to a housing for a turbomachine, wherein the housing includes at least one variable guide vane, which has a pivot pin that is arranged rotatably on the housing and at least one roller bearing. In doing so, it is provided according to the invention that the roller bearing utilized here is constructed according to the first aspect of the invention. The features resulting from this and their advantages are disclosed in the descriptions of the first aspect of the invention, wherein advantageous embodiments of the first aspect of the invention are to be considered as advantageous embodiments of the second aspect of the invention.
In an advantageous embodiment of the invention, it is provided that at least two roller bearings are arranged in the axial direction of the pivot pin above each other on the pivot pin of the at least one guide vane. In this way, a mounting of the guide vane able to withstand particularly high mechanical and thermal loads is created, since two or more smaller roller bearings with smaller tolerances are used instead of a comparatively long roller bearing with correspondingly higher tolerances.
Additional advantages are that the pivot pin of the at least one guide vane is sealed by a shaft seal, particularly by a stuffing box, relative to the housing. In this way, leak-tightness of the entire support of the guide vane is achieved. Due to the precise mounting of the guide vane by the roller bearing according to the invention, it is also ensured that only very few asymmetric leakage gaps occur in the shaft seal, whereby their sealing effect is also maintained across all operating points of an associated turbomachine.
In another advantageous embodiment of the invention, it is provided that the housing includes a guide vane cascade with at least two variable guide vanes. Such adjustable guide vane cascades ensure additionally increased efficiency of the associated turbomachine.
A fourth aspect of the invention relates to a turbomachine, particularly an aircraft engine, which has at least one guide vane according to the second aspect of the invention and/or a housing according to the third aspect of the invention. The features resulting from this and their advantages are disclosed in the descriptions of the second and third aspects of the invention respectively, wherein advantageous embodiments of the second and third aspects of the invention are to be considered as advantageous embodiments of the fourth aspect of the invention.
Additional features of the invention emerge from the following description as well as the drawings. The features and feature combinations precedingly described in the description as well as the features and feature combinations subsequently mentioned in the embodiments are not only usable in the respectively mentioned combination, but also in other combinations, without departing from the scope of the invention.